It is known in the prior art to govern propeller speed by controlling propeller pitch. It is also known to provide dynamic compensation for the propeller speed control which is a function of the propeller speed passed through a lead network. There is however no lead compensation which provides near optimum governor dynamic compensation at both low and high flight speeds.
FIG. 1 illustrates the prior art governor and the improved governor in accordance with this invention. The typical prior art governor consists of an integrator 11 acting on propeller pitch, the propeller and propeller inertia 12. Since the control variable is propeller speed at the output of 12, this term is also fed back to the input at summing junctions 13 and 14. It is also known to incorporate the speed derivative feedback in the propeller electronic SYNCHROPHASER.RTM. which provides a lead compensation in the propeller speed governing loop. This lead compensates for the combined inertia lag of the propeller and power turbine.
Electronic hardware constraints often require that a constant value of the lead time constant (K2), FIG. 1, be used at all operating conditions. It is known that the inertia lag time constant at high flight speeds is much smaller than the time constant at low flight speeds. Selection of the time constant for lead compensation must therefore be compromised to a smaller time constant value for high flight speed stability than the optimal which would be selected for good low flight speed governing characteristics. This results in less than optimum lead compensation during low flight speeds.